Immunocytochemical localization of bovine thyrotropin and thyroid auto-antibodies in porcine thyrocytes.

Interactions of receptor-bound bovine thyrotropin (bTSH) and immunoglobulins G from sera of patients with Graves' (G-IgG) or Hashimoto's (H-IgG) disease with porcine thyrocytes were studied by immunocytochemistry. Porcine thyroid fragments were fixed and prepared for immunoreaction or enzymatically dissociated with collagenase and dispase II. The dispersed cells were cultured in primary monolayer in a hormone-free medium or in a medium with bTSH (150 micrograms/ml) for 7 days. After immunostaining the thyrocytes in fragments and monolayers were stained with periodic acid Schiff (PAS) or with PAS and haemalum. Cultivation of the isolated thyrocytes in bTSH-enriched medium leads to a monolayer with globular aggregates, i.e., reconstructed three-dimensional follicles. Follicular cells in these monolayers and in fragments give a weak to moderate immunoreaction to anti-bTSH and a strong reaction to G-IgG and H-IgG (vs. control IgG). Precipitate is found particularly in the perinuclear area and to a lesser degree throughout the cytoplasm. Cells cultured in the absence of bTSH show minimal immunoreaction to anti-bTSH, but moderate reaction to G-IgG and H-IgG. Preincubation with bTSH leads to a strong reduction of immunoreaction to G-IgG but does not affect reaction to H-IgG. Morphological results indicate that G-IgG and H-IgG interact with the same cellular sites as bTSH. Hashimoto's disease antibodies bind to a determinant on the TSH receptor separate from the one on which TSH and Graves' IgG bind.